Mould fungi in high efficiency particulate air (HEPA) filters in vehicle air supply systems - Part II: Preliminary field study

In the summer of 2001, as a part of a research project on behalf of the Tiefbou-Beruftgenossenschaft (institution for statutory accident insurance and prevention in the civil engineering sector), a series of field tests were carried out over a three-month period to find out whether mould fungi permeate the high-efficiency submicron particle (HEPA) filters widely used in ventilation systems of waste management vehicles. On the untreated air side, mould fungus density in the filter measured between 20 to 1 500 CFU/cm2, with clean air side values ranging from 2. Adhesive film samples were similarly taken both from the untreated and clean air side but these did not show any apparent mould fungus permeation through the filter material. From the field research results presented here, the danger of mould fungus penetrating the sub-micron filter can possibly be considered as given where the vehicle is exposed to constant high humidity over a long period of time and the conditions directly around the filter are also sufficiently humid for a longer period.